taken from:http://www.youtube.com/watch?v=eC-EzLHiO2g

By 1000 BC, the ancient civilizations were using technologies that would form the basis of the various branches of chemistry. Extracting metal from their ores, making pottery and glazes, fermenting beer and wine, making pigments for cosmetics and painting, extracting chemicals from plants for medicine and perfume, making cheese, dying cloth, tanning leather, rendering fat into soap, making glass, and making alloys like bronze.


Taken from: //http://www.infoplease.com/ce6/sci/A0857271.html//


-Robert Voile
-Antoine Lavoisier


Biography:
-http://mgprofil.wordpress.com
-http://en.wikipedia.org

Chemistry is a branch of science that has been around for a long time. In fact, chemistry is known to date back to as far as the prehistoric times. Due to the amount of time chemistry takes up on the timeline, the science is split into four general chronological categories. The four categories are: prehistoric times - beginning of the Christian era (black magic), beginning of the Christian era - end of 17th century (alchemy), end of 17th century - mid 19th century (traditional chemistry) and mid 19th century - present (modern chemistry).
The earliest record of man's interest in chemistry was approximately 3,000 B.C, in the fertile crescent. At that time, chemistry was more an art than a science. Tablets record the first known chemists as women who manufactured perfumes from various substances. Ancient Egyptians produced certain compounds such as those used in mummification. By 1000 B.C, chemical arts included the smelting of metals and the making of drugs, dyes, iron, and bronze. Iron making was also introduced and refinement of lead and mercury was performed. The physical properties of some metals such as copper, zinc, silver, and gold were understood. Many groups of people contributed to these developments--among them were ancient Egyptians, Greeks, Hebrews, Chinese, and Indians.


It was during this time that the roots of alchemy grew. The Greeks of Egypt are regarded as the forefathers of attempts to change valueless metals into metals of greater value (e.g. iron into gold). In the fourth century B.C, tZosimos the Greek described a substance called Xerion, a metal that supposedly turned other metals into gold. One needed to add a little dab of Xerion to a pile of metal and after two hundred years, the metal would have become gold.
This was the extent of the world's knowledge on chemistry. In Europe, it remained so well into the Middle Ages (400-1500 C.E).


Taken From:
- http://chemistry.about.com/od/historyofchemistry/History_of_Chemistry.htm
- http://www.winterhouse.com/vancouver/images/25-unioncarbide-ad.jpg
- http://www.columbia.edu/itc/chemistry/chem-c2507/navbar/chemhist.html
- http://www.albalagh.net/kids/science/chemistry.shtml
- http://www.parmacityschools.org/parma_high/science/images/chemistry_3.jpgthe history of chemistry
The look at the history of chemistry that occurs tries to show that chemistry, like any science, is not sterile, not a theoretical wall timeless, is a historical construction, a drama of ideas that is woven having a social fund to some extent the set.

In this first part briefly covers the major changes originating from suffering the planet until birth and death reorientation of Alchemy through the enormous progress of the ancient world and the contributions of Greek philosophy and the Greco - Roman
//taken from: http://www.monografias.com/trabajos11/histqui//



The History of Chemistry

The earliest record of man's interest in chemistry was approximately 3,000 B.C, in the fertile crescent. At that time, chemistry was more an art than a science. Tablets record the first known chemists as women who manufactured perfumes from various substances. Ancient Egyptians produced certain compounds such as those used in mummification. By 1000 B.C, chemical arts included the smelting of metals and the making of drugs, dyes, iron, and bronze. Iron making was also introduced and refinement of lead and mercury was performed. The physical properties of some metals such as copper, zinc, silver, and gold were understood. Many groups of people contributed to these developments--among them were ancient Egyptians, Greeks, Hebrews, Chinese, and Indians

t__aken from:__ http://www.albalagh.net/kids/science/chemistry.shtml



The history of chemistry
By 1000 BC, the ancient civilizations were using technologies that would form the basis of the various branches of chemistry. Extracting metal from their ores, making pottery and glazes, fermenting beer and wine, making pigments for cosmetics and painting, extracting chemicals from plants for medicine and perfume, making cheese, dying cloth, tanning leather, rendering fat into soap, making glass, and making alloys like bronze.
Philosophical attempts to explain the nature of matter and its transformations failed. The protoscience of alchemy also failed, but by experimentation and recording the results set the stage for science. Modern chemistry begins to emerge when a clear distinction is made between chemistry and alchemy by Robert Boyle in his work The Skeptical Chymist (1661). Chemistry then becomes a full-fledged science when Antoine Lavoisier develops his law of conservation of mass, which demands careful measurements and quantitative observations of chemical phenomena. So, while both alchemy and chemistry are concerned with the nature of matter and its transformations, it is only the chemists who apply the scientific method. The history of chemistry is intertwined with the history of thermodynamics, especially through the work of Willard Gibbs.
Take from: http://en.wikipedia.org/wiki/History_of_chemistry.


The earliest record of man's interest in chemistry was approximately 3,000 B.C, in the fertile crescent. At that time, chemistry was more an art than a science. Tablets record the first known chemists as women who manufactured perfumes from various substances. Ancient Egyptians produced certain compounds such as those used in mummification. By 1000 B.C, chemical arts included the smelting of metals and the making of drugs, dyes, iron, and bronze. Iron making was also introduced and refinement of lead and mercury was performed. The physical properties of some metals such as copper, zinc, silver, and gold were understood. Many groups of people contributed to these developments--among them were ancient Egyptians, Greeks, Hebrews, Chinese, and Indians.
take from:http://www.albalagh.net/kids/science/chemistry.shtml

http://www.columbia.edu/itc/chemistry/chem-c2507/navbar/BEAKERS.GIF

history of chemistry

http://www.columbia.edu/itc/chemistry/chem-c2507/navbar/BEAKERS.GIF

Chemistry is a branch of science that has been around for a long time. In fact, chemistry is known to date back to as far as the prehistoric times. Due to the amount of time chemistry takes up on the timeline, the science is split into four general chronological categories. The four categories are: prehistoric times - beginning of the Christian era (black magic), beginning of the Christian era - end of 17th century (alchemy), end of 17th century - mid 19th century (traditional chemistry) and mid 19th century - present (modern chemistry).






taken from:www.youtube.com/watch?v=25lprEvoFJ8

Chemistry

From Wikipedia, the free encyclopedia

Jump to: navigation, searchFor other uses, see Chemistry (disambiguation).
Chemistry (from Arabic: كيمياء Latinized: chem (kēme), meaning "value")[1] is the science of matter and the changes it undergoes. The science of matter is also addressed by physics, but while physics takes a more general and fundamental approach, chemistry is more specialized - concerned with the composition, behavior, structure, and properties of matter, as well as the changes it undergoes during chemical reactions.[2] It is a physical science for studies of various atoms, molecules, crystals and other aggregates of matter whether in isolation or combination, which incorporates the concepts of energy and entropy in relation to the spontaneity of chemical processes. Modern chemistry evolved out of alchemy and began to develop into its modern form through the 10th Century Arab world and following the chemical revolution (1773).
Disciplines within chemistry are traditionally grouped by the type of matter being studied or the kind of study. These include inorganic chemistry, the study of inorganic matter; organic chemistry, the study of organic matter; biochemistry, the study of substances found in biological organisms; physical chemistry, the energy related studies of chemical systems at macro, molecular and submolecular scales; analytical chemistry, the analysis of material samples to gain an understanding of their chemical composition and structure. Many more specialized disciplines have emerged in recent years, e.g. neurochemistry the chemical study of the nervous system (see subdisciplines).

Summary

Chemistry is the scientific study of interaction of chemical substances[3] that are constituted of atoms or the subatomic particles: protons, electrons and neutrons.[4] Atoms combine to produce molecules or crystals. Chemistry is often called "the central science" because it connects the other natural sciences such as astronomy, physics, material science, biology, and geology.[5][6]
The genesis of chemistry can be traced to certain practices, known as alchemy, which had been practiced for several millennia in various parts of the world, particularly the Middle East.[7]
The structure of objects we commonly use and the properties of the matter we commonly interact with, are a consequence of the properties of chemical substances and their interactions. For example, steel is harder than iron because its atoms are bound together in a more rigid crystalline lattice; wood burns or undergoes rapid oxidation because it can react spontaneously with oxygen in a chemical reaction above a certain temperature; sugar and salt dissolve in water because their molecular/ionic properties are such that dissolution is preferred under the ambient conditions.
The transformations that are studied in chemistry are a result of interaction either between different chemical substances or between matter and energy. Traditional chemistry involves study of interactions between substances in a chemistry laboratory using various forms of laboratory glassware.
Laboratory, Institute of Biochemistry, University of Cologne
A chemical reaction is a transformation of some substances into one or more other substances.[8] It can be symbolically depicted through a chemical equation. The number of atoms on the left and the right in the equation for a chemical transformation is most often equal. The nature of chemical reactions a substance may undergo and the energy changes that may accompany it are constrained by certain basic rules, known as chemical laws.
Energy and entropy considerations are invariably important in almost all chemical studies. Chemical substances are classified in terms of their structure, phase as well as their chemical compositions. They can be analyzed using the tools of chemical analysis, e.g. spectroscopy and chromatography.
Chemistry is an integral part of the science curriculum both at the high school as well as the early college level. At these levels, it is often called "general chemistry" which is an introduction to a wide variety of fundamental concepts that enable the student to acquire tools and skills useful at the advanced levels, whereby chemistry is invariably studied in any of its various sub-disciplines. Scientists, engaged in chemical research are known as chemists.[9] Most chemists specialize in one or more sub-disciplines.

History

Main article: History of chemistrySee also: Alchemy, Timeline of chemistry, and Nobel Prize in Chemistry
Ancient Egyptians pioneered the art of synthetic "wet" chemistry up to 4,000 years ago.[10] By 1000 BC ancient civilizations were using technologies that formed the basis of the various branches of chemistry such as; extracting metal from their ores, making pottery and glazes, fermenting beer and wine, making pigments for cosmetics and painting, extracting chemicals from plants for medicine and perfume, making cheese, dying cloth, tanning leather, rendering fat into soap, making glass, and making alloys like bronze.
The genesis of chemistry can be traced to the widely observed phenomenon of burning that led to metallurgy—the art and science of processing ores to get metals (e.g. metallurgy in ancient India). The greed for gold led to the discovery of the process for its purification, even though the underlying principles were not well understood—it was thought to be a transformation rather than purification. Many scholars in those days thought it reasonable to believe that there exist means for transforming cheaper (base) metals into gold. This gave way to alchemy and the search for the Philosopher's Stone which was believed to bring about such a transformation by mere touch.[11]
Greek atomism dates back to 440 BC, as what might be indicated by the book De Rerum Natura (The Nature of Things)[12] written by the Roman Lucretius[13] in 50 BC. Much of the early development of purification methods is described by Pliny the Elder in his Naturalis Historia.
A tentative outline is as follows:

1. Egyptian alchemy [3,000 BCE – 400 BCE], formulate early "element" theories such as the Ogdoad.
2. Greek alchemy [332 BCE – 642 CE], the Greek king Alexander the Great conquers Egypt and founds Alexandria, having the world's largest library, where scholars and wise men gather to study.
3. Arab alchemy [642 CE – 1200], the Muslim conquest of Egypt (primarily Alexandria); development of the Scientific Method by Alhazen and Jābir ibn Hayyān revolutionise the field of Chemistry.
4. The House of Wisdom (Arabic: بيت الحكمة‎; Bait al-Hikma), Al-Andalus (Arabic: الأندلس‎) and Alexandria (Arabic: الإسكندرية) become the world leading institutions where scientists of all religious and ethnic backgrounds worked together in harmony expanding the reaches of Chemistry in a time known as the Islamic Golden Age.
5. Jābir ibn Hayyān, al-Kindi, al-Razi, al-Biruni and Alhazen continue to dominate the field of Chemistry, mastering it and expanding the boundaries of knowledge and experimentation.
6. European alchemy [1300 – present], Pseudo-Geber builds on Arabic chemistry.
7. Chemistry [1661], Boyle writes his classic chemistry text The Sceptical Chymist.
8. Chemistry [1787], Lavoisier writes his classic Elements of Chemistry.
9. Chemistry [1803], Dalton publishes his Atomic Theory.

The earliest pioneers of Chemistry, and inventors of the modern scientific method, were medieval Arab and Persian scholars. They introduced precise observation and controlled experimentation into the field and discovered numerous Chemical substances.[14]

"Chemistry as a science was almost created by the Muslims; for in this field, where the Greeks (so far as we know) were confined to industrial experience and vague hypothesis, the Saracens introduced precise observation, controlled experiment, and careful records. They invented and named the alembic (al-anbiq), chemically analyzed innumerable substances, composed lapidaries, distinguished alkalis and acids, investigated their affinities, studied and manufactured hundreds of drugs. Alchemy, which the Muslims inherited from Egypt, contributed to chemistry by a thousand incidental discoveries, and by its method, which was the most scientific of all medieval operations."
[15]
The most influential Muslim chemists were Geber (d. 815), al-Kindi (d. 873), al-Razi (d. 925), al-Biruni (d. 1048) and Alhazen (d. 1039).[16] The works of Geber became more widely known in Europe through Latin translations by a pseudo-Geber in 14th century Spain, who also wrote some of his own books under the pen name "Geber". The contribution of Indian alchemists and metallurgists in the development of chemistry was also quite significant.[17]
The emergence of chemistry in Europe was primarily due to the recurrent incidence of the plague and blights there during the so called Dark Ages. This gave rise to a need for medicines. It was thought that there exists a universal medicine called the Elixir of Life that can cure all diseases, but like the Philosopher's Stone, it was never found.
For some practitioners, alchemy was an intellectual pursuit, over time, they got better at it. Paracelsus (1493–1541), for example, rejected the 4-elemental theory and with only a vague understanding of his chemicals and medicines, formed a hybrid of alchemy and science in what was to be called iatrochemistry. Similarly, the influences of philosophers such as Sir Francis Bacon (1561–1626) and René Descartes (1596–1650), who demanded more rigor in mathematics and in removing bias from scientific observations, led to a scientific revolution. In chemistry, this began with Robert Boyle (1627–1691), who came up with an equation known as Boyle's Law about the characteristics of gaseous state.[18] Chemistry indeed came of age when Antoine Lavoisier (1743–1794), developed the theory of Conservation of mass in 1783; and the development of the Atomic Theory by John Dalton around 1800. The Law of Conservation of Mass resulted in the reformulation of chemistry based on this law and the oxygen theory of combustion, which was largely based on the work of Lavoisier. Lavoisier's fundamental contributions to chemistry were a result of a conscious effort to fit all experiments into the framework of a single theory. He established the consistent use of the chemical balance, used oxygen to overthrow the phlogiston theory, and developed a new system of chemical nomenclature and made contribution to the modern metric system. Lavoisier also worked to translate the archaic and technical language of chemistry into something that could be easily understood by the largely uneducated masses, leading to an increased public interest in chemistry. All these advances in chemistry led to what is usually called the chemical revolution. The contributions of Lavoisier led to what is now called modern chemistry—the chemistry that is studied in educational institutions all over the world. It is because of these and other contributions that Antoine Lavoisier is often celebrated as the "Father of Modern Chemistry".[19] The later discovery of Friedrich Wöhler that many natural substances, organic compounds, can indeed be synthesized in a chemistry laboratory also helped the modern chemistry to mature from its infancy.[20]
The discovery of the chemical elements has a long history from the days of alchemy and culminating in the discovery of the periodic table of the chemical elements by Dmitri Mendeleev (1834–1907)[21] and later discoveries of some synthetic elements.

Etymology

Main article: Chemistry (etymology)
The word chemistry comes from the earlier study of alchemy, which is a set of practices that encompasses elements of chemistry, metallurgy, philosophy, astrology, astronomy, mysticism and medicine. Alchemy in turn is derived from the Arabic word "كيمياء" meaning "value", it is commonly thought of as the quest to turn lead or another common starting material into gold.[22] This linguistic relation between the pursuit of value and alchemy is thought to have Egyptian origins. Many believe that the Arabic word "alchemy" is derived from the word Chemi or Kimi, which is the ancient name of Egypt in Egyptian.[23][24][25] The word was subsequently borrowed by the Greeks, and from the Greeks by the Arabs when they occupied Alexandria (Egypt) in the 7th century. The Arabs added the Arabic definite article "al" to the word, resulting in the word "الكيمياء" (al-kīmiyā). Thus, an alchemist was called a 'chemist' in popular speech, and later the suffix "-ry" was added to this to describe the art of the chemist as "chemistry".

Definitions

In retrospect, the definition of chemistry seems to invariably change per decade, as new discoveries and theories add to the functionality of the science. Shown below are some of the standard definitions used by various noted chemists:

• Alchemy (330) – the study of the composition of waters, movement, growth, embodying, disembodying, drawing the spirits from bodies and bonding the spirits within bodies (Zosimos).[26]
• Chymistry (1661) – the subject of the material principles of mixt bodies (Boyle).[27]
• Chymistry (1663) – a scientific art, by which one learns to dissolve bodies, and draw from them the different substances on their composition, and how to unite them again, and exalt them to a higher perfection (Glaser).[28]
• Chemistry (1730) – the art of resolving mixt, compound, or aggregate bodies into their principles; and of composing such bodies from those principles (Stahl).[29]
• Chemistry (1837) – the science concerned with the laws and effects of molecular forces (Dumas).[30]
• Chemistry (1947) – the science of substances: their structure, their properties, and the reactions that change them into other substances (Pauling).[31]
• Chemistry (1998) – the study of matter and the changes it undergoes (Chang).[32].

Basic concepts

Several concepts are essential for the study of chemistry; some of them are:[33]

Atom

Main article: Atom
An atom is the basic unit of chemistry. It consists of a positively charged core (the atomic nucleus) which contains protons and neutrons, and which maintains a number of electrons to balance the positive charge in the nucleus. The atom is also the smallest entity that can be envisaged to retain some of the chemical properties of the element, such as electronegativity, ionization potential, preferred oxidation state(s), coordination number, and preferred types of bonds to form (e.g., metallic, ionic, covalent).

Element

Main article: Chemical element
The concept of chemical element is related to that of chemical substance. A chemical element is characterized by a particular number of protons in the nuclei of its atoms. This number is known as the atomic number of the element. For example, all atoms with 6 protons in their nuclei are atoms of the chemical element carbon, and all atoms with 92 protons in their nuclei are atoms of the element uranium. 94 different chemical elements or types of atoms based on the number of protons exist naturally. A further 18 have been recognised by IUPAC as existing artificially only. Although all the nuclei of all atoms belonging to one element will have the same number of protons, they may not necessarily have the same number of neutrons, such atoms are termed isotopes. In fact several isotopes of an element may exist.
The most convenient presentation of the chemical elements is in the periodic table of the chemical elements, which groups elements by atomic number. Due to its ingenious arrangement, groups, or columns, and periods, or rows, of elements in the table either share several chemical properties, or follow a certain trend in characteristics such as atomic radius, electronegativity, etc. Lists of the elements by name, by symbol, and by atomic number are also available.

Compound

Main article: Chemical compound
A compound is a substance with a particular ratio of atoms of particular chemical elements which determines its composition, and a particular organization which determines chemical properties. For example, water is a compound containing hydrogen and oxygen in the ratio of two to one, with the oxygen atom between the two hydrogen atoms, and an angle of 104.5° between them. Compounds are formed and interconverted by chemical reactions.

Substance

Main article: Chemical substance
A chemical substance is a kind of matter with a definite composition and set of properties.[34] Strictly speaking, a mixture of compounds, elements or compounds and elements is not a chemical substance, but it may be called a chemical. Most of the substances we encounter in our daily life are some kind of mixture; for example: air, alloys, biomass, etc.
Nomenclature of substances is a critical part of the language of chemistry. Generally it refers to a system for naming chemical compounds. Earlier in the history of chemistry substances were given name by their discoverer, which often led to some confusion and difficulty. However, today the IUPAC system of chemical nomenclature allows chemists to specify by name specific compounds amongst the vast variety of possible chemicals. The standard nomenclature of chemical substances is set by the International Union of Pure and Applied Chemistry (IUPAC). There are well-defined systems in place for naming chemical species. Organic compounds are named according to the organic nomenclature system.[35] Inorganic compounds are named according to the inorganic nomenclature system.[36] In addition the Chemical Abstracts Service has devised a method to index chemical substance. In this scheme each chemical substance is identifiable by a number known as CAS registry number.

Molecule

Main article: Molecule
A molecule is the smallest indivisible portion, besides an atom, of a pure chemical substance that has its unique set of chemical properties, that is, its potential to undergo a certain set of chemical reactions with other substances. Molecules can exist as electrically neutral units unlike ions. Molecules are typically a set of atoms bound together by covalent bonds, such that the structure is electrically neutral and all valence electrons are paired with other electrons either in bonds or in lone pairs.
A molecular structure depicts the bonds and relative positions of atoms in a molecule such as that in Paclitaxel shown here.
One of the main characteristic of a molecule is its geometry often called its structure. While the structure of diatomic, triatomic or tetra atomic molecules may be trivial, (linear, angular pyramidal etc.) the structure of polyatomic molecules, that are constituted of more than six atoms (of several elements) can be crucial for its chemical nature.

Mole

Main article: Mole (unit)
A mole is the amount of a substance that contains as many elementary entities (atoms, molecules or ions) as there are atoms in 0.012 kilogram (or 12 grams) of carbon-12, where the carbon-12 atoms are unbound, at rest and in their ground state.[37] This number is known as the Avogadro constant, and is determined empirically. The currently accepted value is 6.02214179(30) × 1023 mol−1 (2007 CODATA). The best way to understand the meaning of the term "mole" is to compare it to terms such as dozen. Just as one dozen is equal to 12, one mole is equal to 6.02214179(30) × 1023. The term is used because it is much easier to say, for example, 1 mole of carbon atoms, than it is to say 6.02214179(30) × 1023 carbon atoms. Likewise, we can describe the number of entities as a multiple or fraction of 1 mole, e.g. 2 mole or 0.5 moles. Mole is an absolute number (having no units) and can describe any type of elementary object, although the mole's use is usually limited to measurement of subatomic, atomic, and molecular structures.
The number of moles of a substance in one liter of a solution is known as its molarity. Molarity is the common unit used to express the concentration of a solution in physical chemistry.

Ions and salts

Main article: Ion
An ion is a charged species, an atom or a molecule, that has lost or gained one or more electrons. Positively charged cations (e.g. sodium cation Na+) and negatively charged anions (e.g. chloride Cl−) can form a crystalline lattice of neutral salts (e.g. sodium chloride NaCl). Examples of polyatomic ions that do not split up during acid-base reactions are hydroxide (OH−) and phosphate (PO43−).
Ions in the gaseous phase is often known as plasma.

Acidity and basicity

Main article: Acid
A substance can often be classified as an acid or a base. This is often done on the basis of a particular kind of reaction, namely the exchange of protons between chemical compounds. However, an extension to this mode of classification was brewed up by the American chemist, Gilbert Newton Lewis; in this mode of classification the reaction is not limited to those occurring in an aqueous solution, thus is no longer limited to solutions in water. According to concept as per Lewis, the crucial things being exchanged are charges[38]. There are several other ways in which a substance may be classified as an acid or a base, as is evident in the history of this concept [39]

Phase

Main article: Phase (matter)
In addition to the specific chemical properties that distinguish different chemical classifications chemicals can exist in several phases. For the most part, the chemical classifications are independent of these bulk phase classifications; however, some more exotic phases are incompatible with certain chemical properties. A phase is a set of states of a chemical system that have similar bulk structural properties, over a range of conditions, such as pressure or temperature. Physical properties, such as density and refractive index tend to fall within values characteristic of the phase. The phase of matter is defined by the phase transition, which is when energy put into or taken out of the system goes into rearranging the structure of the system, instead of changing the bulk conditions.
Sometimes the distinction between phases can be continuous instead of having a discrete boundary, in this case the matter is considered to be in a supercritical state. When three states meet based on the conditions, it is known as a triple point and since this is invariant, it is a convenient way to define a set of conditions.
The most familiar examples of phases are solids, liquids, and gases. Many substances exhibit multiple solid phases. For example, there are three phases of solid iron (alpha, gamma, and delta) that vary based on temperature and pressure. A principal difference between solid phases is the crystal structure, or arrangement, of the atoms. Another phase commonly encountered in the study of chemistry is the aqueous phase, whihch is the state of substances dissolved in aqueous solution (that is, in water). Less familiar phases include plasmas, Bose-Einstein condensates and fermionic condensates and the paramagnetic and ferromagnetic phases of magnetic materials. While most familiar phases deal with three-dimensional systems, it is also possible to define analogs in two-dimensional systems, which has received attention for its relevance to systems in biology.

Redox

Main article: Redox
It is a concept related to the ability of atoms of various substances to lose or gain electrons. Substances that have the ability to oxidize other substances are said to be oxidative and are known as oxidizing agents, oxidants or oxidizers. An oxidant removes electrons from another substance. Similarly, substances that have the ability to reduce other substances are said to be reductive and are known as reducing agents, reductants, or reducers. A reductant transfers electrons to another substance, and is thus oxidized itself. And because it "donates" electrons it is also called an electron donor. Oxidation and reduction properly refer to a change in oxidation number—the actual transfer of electrons may never occur. Thus, oxidation is better defined as an increase in oxidation number, and reduction as a decrease in oxidation number.

Bonding

Main article: Chemical bondElectron atomic and molecular orbitals
Atoms sticking together in molecules or crystals are said to be bonded with one another. A chemical bond may be visualized as the multipole balance between the positive charges in the nuclei and the negative charges oscillating about them.[40] More than simple attraction and repulsion, the energies and distributions characterize the availability of an electron to bond to another atom. These potentials create the interactions which hold atoms together in molecules or crystals. In many simple compounds, Valence Bond Theory, the Valence Shell Electron Pair Repulsion model (VSEPR), and the concept of oxidation number can be used to explain molecular structure and composition. Similarly, theories from classical physics can be used to predict many ionic structures. With more complicated compounds, such as metal complexes, valence bond theory fails and alternative approaches, primarily based on principles of quantum chemistry such as the molecular orbital theory, are necessary. See diagram on electronic orbitals.

Reaction

Main article: Chemical reaction
When a chemical substance is transformed as a result of its interaction with another a chemical reaction is said to have occurred. Chemical reaction is a therefore a concept related to transformations of chemical substances through interactions. It results in some energy exchange between the constituents of the reaction as well with the system environment which may be a designed vessels which are often laboratory glassware. Chemical reactions can result in the formation or dissociation of molecules, that is, molecules breaking apart to form two or more smaller molecules, or rearrangement of atoms within or across molecules. Chemical reactions usually involve the making or breaking of chemical bonds. Oxidation, reduction, dissociation, acid-base neutralization and molecular rearrangement are some of the commonly used kinds of chemical reactions.
A chemical reaction can be symbolically depicted through a chemical equation. While in a non-nuclear chemical reaction the number and kind of atoms on both sides of the equation are equal, for a nuclear reaction this holds true only for the nuclear particles viz. protons and neutrons.[41]
The sequence of steps in which the reorganization of chemical bonds may be taking place in the course of a chemical reaction is called its mechanism. A chemical reaction can be envisioned to take place in a number of steps, each of which may have a different speed. Many reaction intermediates with variable stability can thus be envisaged during the course of a reaction. Reaction mechanisms are proposed to explain the kinetics and the relative product mix of a reaction. Many physical chemists specialize in exploring and proposing the mechanisms of various chemical reactions. Several empirical rules, like the Woodward-Hoffmann rules often come handy while proposing a mechanism for a chemical reaction.
A stricter definition is that "a chemical reaction is a process that results in the interconversion of chemical species".[42] Under this definition, a chemical reaction may be an elementary reaction or a stepwise reaction. An additional caveat is made, in that this definition includes cases where the interconversion of conformers is experimentally observable. Such detectable chemical reactions normally involve sets of molecular entities as indicated by this definition, but it is often conceptually convenient to use the term also for changes involving single molecular entities (i.e. 'microscopic chemical events').

Equilibrium

Main article: Chemical equilibrium
Although the concept of equilibrium is widely used across sciences, in the context of chemistry, it arises whenever a number of different states of the chemical composition are possible. For example, in a mixture of several chemical compounds that can react with one another, or when a substance can be present in more then one kind of phase. The concept is used to describe the state in which the parameters such as chemical composition remains unchanged over time. Chemicals present in biological systems are invariably not at equilibrium, rather they are far from equilibrium.

Energy

Main article: Energy
In the context of chemistry, energy is an attribute of a substance as a consequence of its atomic, molecular or aggregate structure. Since a chemical transformation is accompanied by a change in one or more of these kinds of structure, it is invariably accompanied by an increase or decrease of energy of the substances involved. Some energy is transferred between the surroundings and the reactants of the reaction in the form of heat or light; thus the products of a reaction may have more or less energy than the reactants. A reaction is said to be exothermic if the final state is lower on the energy scale than the initial state; in the case of endothermic reactions the situation is otherwise.
Chemical reactions are invariably not possible unless the reactants surmount an energy barrier known as the activation energy. The speed of a chemical reaction (at given temperature T) is related to the activation energy E, by the Boltzmann's population factor e − E / kT - that is the probability of molecule to have energy greater than or equal to E at the given temperature T. This exponential dependence of a reaction rate on temperature is known as the Arrhenius equation. The activation energy necessary for a chemical reaction can be in the form of heat, light, electricity or mechanical force in the form of ultrasound.[43]
A related concept free energy, which also incorporates entropy considerations, is a very useful means for predicting the feasibility of a reaction and determining the state of equilibrium of a chemical reaction, in chemical thermodynamics. A reaction is feasible only if the total change in the Gibbs free energy is negative,

Delta G le 0 ,

; if it is equal to zero the chemical reaction is said to be at equilibrium.
There exist only limited possible states of energy for electrons, atoms and molecules. These are determined by the rules of quantum mechanics, which require quantization of energy of a bound system. The atoms/molecules in a higher energy state are said to be excited. The molecules/atoms of substance in an excited energy state are often much more reactive; that is, more amenable to chemical reactions.
The phase of a substance is invariably determined by its energy and the energy of its surroundings. When the intermolecular forces of a substance are such that the energy of the surroundings is not sufficient to overcome them, it occurs in a more ordered phase like liquid or solid as is the case with water (H2O); a liquid at room temperature because its molecules are bound by hydrogen bonds.[44] Whereas hydrogen sulfide (H2S) is a gas at room temperature and standard pressure, as its molecules are bound by weaker dipole-dipole interactions.
The transfer of energy from one chemical substance to another depends on the size of energy quanta emitted from one substance. However, heat energy is often transferred more easily from almost any substance to another because the phonons responsible for vibrational and rotational energy levels in a substance have much less energy than photons invoked for the electronic energy transfer. Thus, because vibrational and rotational energy levels are more closely spaced than electronic energy levels, heat is more easily transferred between substances relative to light or other forms of electronic energy. For example, ultraviolet electromagnetic radiation is not transferred with as much efficacy from one substance to another as thermal or electrical energy.
The existence of characteristic energy levels for different chemical substances is useful for their identification by the analysis of spectral lines. Different kinds of spectra are often used in chemical spectroscopy, e.g. IR, microwave, NMR, ESR, etc. Spectroscopy is also used to identify the composition of remote objects - like stars and distant galaxies - by analyzing their radiation spectra.
Emission spectrum of iron
The term chemical energy is often used to indicate the potential of a chemical substance to undergo a transformation through a chemical reaction or to transform other chemical substances.

Taken from:http://en.wikipedia.org/wiki/Chemistry



this is a atom
taken from:
//http://www.napavalley.edu/Academics/SME/Chemistry/PublishingImages/chemistry_molecules.gif//





Alchemy
It was during this time that the roots of alchemy grew. The Greeks of Egypt are regarded as the forefathers of attempts to change valueless metals into metals of greater value (e.g. iron into gold). In the fourth century B.C, Zosimos the Greek described a substance called Xerion, a metal that supposedly turned other metals into gold. One needed to add a little dab of Xerion to a pile of metal and after two hundred years, the metal would have become gold.
This was the extent of the world's knowledge on chemistry. In Europe, it remained so well into the Middle Ages (400-1500 C.E).


Alchemists (~1000-1650)
Among other things, the alchemists sought a universal solvent, attempted to change lead and other metals into gold, and tried to discover an elixir which would prolong life.The alchemists learned how to use metallic compounds and plant-derived materials to treat diseases.

Torricelli, Evangelista (1643)
Invented the mercury barometer .

cheele, C.W. (1742-1786)
Discovered chlorine, tartaric acid, metal oxidation, and sensitivity of silver compounds to light (photochemistry).

Franklin , Benjamin (1752)
Demonstrated that lightning is electricity .



Taken from http://chemistry.about.com/cs/history/a/aa020204a.htm
taken from://**//http://www.scientific-web.com/en/Physics/Biographies/images/Torricelli.jpg//**//
taken from:http://scrapetv.com/News/News%20Pages/usa/images-4/benjamin-franklin.jpg





In prehistoric times chemistry was more an art than a science, after the chemical revolution of the 18th century it became a real science and now it is an important part of our daily lives. However, chemistry has a negative perception in public opinion. It is seen as bad for people and damaging to the environment, the industrial contamination and disasters have a negative impact on public opinion.

taken from:http://www.google.com/search?hl=en&gbv=2&as_q=history+of+chemistry&as_epq=&as_oq=&as_eq=&num=30&lr=&as_filetype=doc&ft=i&as_sitesearch=&as_qdr=all&as_rights=&as_occt=any&cr=&as_nlo=&as_nhi=&safe=images

taken from:http://www.google.com/search?hl=en&gbv=2&as_q=history+of+chemistry&as_epq=&as_oq=&as_eq=&num=30&lr=&as_filetype=doc&ft=i&as_sitesearch=&as_qdr=all&as_rights=&as_occt=any&cr=&as_nlo=&as_nhi=&safe=images

taken from:http://www.unomaha.edu/chemistry/web%20images/chemistry.jpg


the modern definition of chemistry

Classically, before the 20th century, chemistry was defined as the science of the nature of matter and its transformations. It was therefore clearly distinct from physics which was not concerned with such dramatic transformation of matter. Moreover, in contrast to physics, chemistry was not using much of mathematics. Even some were particularly reluctant to using mathematics within chemistry. For example, Auguste Comte wrote in 1830:

Every attempt to employ mathematical methods in the study of chemical questions must be considered profoundly irrational and contrary to the spirit of chemistry.... if mathematical analysis should ever hold a prominent place in chemistry -- an aberration which is happily almost impossible -- it would occasion a rapid and widespread degeneration of that science.
However, in the second part of the 19th century, the situation changed and August Kekule wrote in 1867:

I rather expect that we shall someday find a mathematico-mechanical explanation for what we now call atoms which will render an account of their properties.
After the discovery by Ernest Rutherford and Niels Bohr of the atomic structure in 1912, and by Marie and Pierre Curie of radioactivity, scientists had to change their viewpoint on the nature of matter. The experience acquired by chemists was no longer pertinent to the study of the whole nature of matter but only to aspects related to the electron cloud surrounding the atomic nuclei and the movement of the latter in the electric field induced by the former (see Born-Oppenheimer approximation). The range of chemistry was thus restricted to the nature of matter around us in conditions which are not too far (or exceptionally far) from standard conditions for temperature and pressure and in cases where the exposure to radiation is not too different from the natural microwave, visible or UV radiations on Earth. Chemistry was therefore re-defined as the science of matter that deals with the composition, structure, and properties of substances and with the transformations that they undergo.[citation needed] However the meaning of matter used here relates explicitly to substances made of atoms and molecules, disregarding the matter within the atomic nuclei and its nuclear reaction or matter within highly ionized plasmas. This does not mean that chemistry is never involved with plasma or nuclear sciences or even bosonic fields nowadays, since areas such as Quantum Chemistry and Nuclear Chemistry are currently well developed and formally recognized sub-fields of study under the Chemical sciences (Chemistry), but what is now formally recognized as subject of study under the Chemistry category as a science is always based

on the use of concepts that describe or explain phenomena either from matter or to matter in the atomic or molecular scale, including the study of the behavior of many molecules as an aggregate or the study of the effects of a single proton on an single atom, but excluding phenomena that deal with different (more "exotic") types of matter (e.g. Bose-Einstein condensate, Higgs Boson, dark matter, naked singularity, etc.) and excluding principles that refer to intrinsic abstract laws of nature in which their concepts can be formulated completely without a precise formal molecular or atomic paradigmatic view (e.g. Quantum Chromodynamics, Quantum Electrodynamics, String Theory, parts of Cosmology (see Cosmochemistry), certain areas of Nuclear Physics (see Nuclear Chemistry),etc.). Nevertheless the field of chemistry is still, on our human scale, very broad and the claim that chemistry is everywhere is accurate.





















taken from:http://en.wikipedia.org/wiki/History_of_chemistry


Achemy
Alchemy, originally derived from the Ancient Greek word khemia (Χημία) meaning "art of transmuting metals", later arabicized as al-kimia (الكيمياء), is both a philosophy and an ancient practice focused on the attempt to change base metals into gold, investigating the preparation of the "elixir of longevity", and achieving ultimate wisdom, involving the improvement of the alchemist as well as the making of several substances described as possessing unusual properties.[1] The practical aspect of alchemy generated the basics of modern inorganic chemistry, namely concerning procedures, equipment and the identification and use of many current substances.
Alchemy has been practiced in Mesopotamia (comprising much of today's Iraq), Egypt, Persia (today's Iran), India, China, Japan, Korea and in Classical Greece and Rome, in the Post-Islamic Persia, and then in Europe up to the 20th century, in a complex network of schools and philosophical systems spanning at least 22500 years

taken from: http://en.wikipedia.org/wiki/Alchemy

The History of Chemistry The earliest record of man's interest in chemistry was approximately 3,000 B.C, in the fertile crescent. At that time, chemistry was more an art than a science. Tablets record the first known chemists as women who manufactured perfumes from various substances. Ancient Egyptians produced certain compounds such as those used in mummification. By 1000 B.C, chemical arts included the smelting of metals and the making of drugs, dyes, iron, and bronze. Iron making was also introduced and refinement of lead and mercury was performed. The physical properties of some metals such as copper, zinc, silver, and gold were understood. Many groups of people contributed to these developments--among them were ancient Egyptians, Greeks, Hebrews, Chinese, and Indians. Alchemy It was during this time that the roots of alchemy grew. The Greeks of Egypt are regarded as the forefathers of attempts to change valueless metals into metals of greater value (e.g. iron into gold). In the fourth century B.C, Zosimos the Greek described a substance called Xerion, a metal that supposedly turned other metals into gold. One needed to add a little dab of Xerion to a pile of metal and after two hundred years, the metal would have become gold. This was the extent of the world's knowledge on chemistry. In Europe, it remained so well into the Middle Ages (400-1500 C.E). The Coming of Islam Yet at that time, a new empire was forming. Islam was spreading among the people of Arabia. At 632 C.E when Prophet Muhammad, Sall-Allahu alayhi wa sallam, died, nearly all of Arabia had become Muslim. Islam had raised these people from ignorance and darkness into light. The Muslims started to become the most advanced civilization of that time. Though Greeks are shown as wise people who had spectacular achievements in science, Muslims are portrayed as alchemists and transmitters of Greek "wisdom", and Western scientists are shown as the real founders of chemistry, the truth is actually the opposite. It is true that Muslims translated many books and writings of the ancients. However, Muslims soon realized that in the field of chemistry the ancients, mainly being alchemists, dealt primarily with speculation and mystery. Chemistry was not a science before the Muslims. The Muslims invented the scientific method and used it in their research tremendously. The historian Briffault's book, Making of Humanity, has been quoted in Dr. K Ajram's book, The Miracle of Islam Science: "Investigation, accumulation of positive knowledge, minute methods of science and prolonged observation were alien to Greek temperament. These were introduced to Europe by the Arabs. European science owes its existence to the Arabs." Will Durant notes that Muslims "introduced precise observation, controlled experiment, and careful records." Work of Muslims Muslims were not alchemists, but rather they were the world's first true chemists. They produced a variety of compounds useful for the development and advancement of science, culture, industry, and civilization. Muslims invented and/or perfected the processes of distillation, sublimation, crystallization, oxidation, and precipitation. They discovered the process of calcination, which is used to reduce substances to a powdered form. Muslims also discovered many elements with their specific weights. Al-Jabr (d. 815?) discovered 19 elements along with their specific weights. They also were the first to accurately divide the elements. Muslims distinguished between metals and alloys, noting that alloys were only mixtures and not true elements. They originated the synthesis of numerous crucial substances that are essential to the development of chemical sciences. The acid-base principal of chemistry was entirely their development. The pH scale was their invention. Evidence is found in the fact that the word alkali originated from the Arabic word al-kili. They invented the concept of solutions regarding the solubility or insolubility of substances. Industrial Chemistry As industrial chemists, Muslims used advanced techniques for extracting minerals and metals. They perfected glass making and introduced the technology for coloring it with metal oxides. They invented crystal making. They introduced and perfected steel making. They produced dyes and used them in tiles, woodworking, and clothing. They produced a variety of plasters, glazes, and other building compounds. Muslim Spain had roads paved with cement instead of stones and had the world's first street lights. Instruments Muslims invented and/or widely used many chemical instruments that are used until now. They used burners, water baths, bellows, crucibles, distillation apparatuses, scales and weights, beakers, filters, flasks, phials, test tubes, etc. Production of Paper Muslims also perfected the production of paper. This accomplishment is often attributed to the Chinese. Though it is true that the Chinese produced paper, this was done through a tedious process requiring silk. It was the Muslims who instituted chemically-aided paper production. The first paper-manufacturing plant in the Muslim World was opened in Baghdad in 794 C.E. Millions upon millions of books were published wherever this invention arrived. In 891 C.E., Baghdad had over a hundred booksellers. Most mosques had libraries. Many cities also had public libraries. Baghdad at the time of the Mongols' invasion had thirty-six libraries. Private libraries were innumerable; it was common for rich people to have huge collections of books. Princes, according to Will Durant, "in the tenth century might own as many books as could be found in all the libraries of Europe combined." Slowly but steadily, Europeans became accustomed to the luxury of imported paper from the Muslim world. Paper was used in Constantinople by 1100, in Sicily by 1102, in Italy by 1154, in Germany by 1228, and in England by 1309. The production of the many cheap books by Europeans was only possible after the replacement of parchment and silk paper with this new paper. The Western world slowly rose from the coffins of illiteracy in which it had been sinking. Muslims' Writings and Books Muslims' writings and books spurred and strongly stimulated the development of European chemistry. Translated versions of Al-Jabr's works were, according to Mathe, Lavoisier's "bible." Ar-Razi's (d. 925) booklet, Secret of Secrets, is said to be the first known example of a chemistry lab manual. Their books were used in many European schools for many centuries. After the Crusades, especially, as returning Western soldiers told fantastic tales of the Muslim World and all the knowledge that was there, Europeans wanted to learn more and their thirst for knowledge grew. Many books were translated into European languages. Slowly, the Western World acquired the knowledge of Muslims, and began its Renaissance. Bibliography Ajram, K. 1992. The Miracle of Islamic Science. Knowledge House Publishers. Durant, Will. 1950. The Age of Faith. New York: Simon and Schuster.

[[kids/|Albalagh Children Home]] [[image:../display/arrow.gif width="25" height="12"]] [[./|Science]] [[image:../display/arrow.gif width="25" height="12"]] The History of Chemistry

http://www.albalagh.net/kids/science/chemistry.shtml

No Copyright Notice. All the material appearing on this web site can be freely distributed for non-commercial purposes. Acknowledgement will be appreciated. The audio files may be copied to tapes, etc. for your listening convenience.

The History of Chemistry
The earliest record of man's interest in chemistry was approximately 3,000 B.C, in the fertile crescent. At that time, chemistry was more an art than a science. Tablets record the first known chemists as women who manufactured perfumes from various substances. Ancient Egyptians produced certain compounds such as those used in mummification. By 1000 B.C, chemical arts included the smelting of metals and the making of drugs, dyes, iron, and bronze. Iron making was also introduced and refinement of lead and mercury was performed. The physical properties of some metals such as copper, zinc, silver, and gold were understood. Many groups of people contributed to these developments--among them were ancient Egyptians, Greeks, Hebrews, Chinese, and Indians.
Alchemy
It was during this time that the roots of alchemy grew. The Greeks of Egypt are regarded as the forefathers of attempts to change valueless metals into metals of greater value (e.g. iron into gold). In the fourth century B.C, Zosimos the Greek described a substance called Xerion, a metal that supposedly turned other metals into gold. One needed to add a little dab of Xerion to a pile of metal and after two hundred years, the metal would have become gold.
This was the extent of the world's knowledge on chemistry. In Europe, it remained so well into the Middle Ages (400-1500 C.E).
The Coming of Islam
Yet at that time, a new empire was forming. Islam was spreading among the people of Arabia. At 632 C.E when Prophet Muhammad, Sall-Allahu alayhi wa sallam, died, nearly all of Arabia had become Muslim. Islam had raised these people from ignorance and darkness into light. The Muslims started to become the most advanced civilization of that time.
Though Greeks are shown as wise people who had spectacular achievements in science, Muslims are portrayed as alchemists and transmitters of Greek "wisdom", and Western scientists are shown as the real founders of chemistry, the truth is actually the opposite. It is true that Muslims translated many books and writings of the ancients. However, Muslims soon realized that in the field of chemistry the ancients, mainly being alchemists, dealt primarily with speculation and mystery. Chemistry was not a science before the Muslims. The Muslims invented the scientific method and used it in their research tremendously. The historian Briffault's book, Making of Humanity, has been quoted in Dr. K Ajram's book, The Miracle of Islam Science: "Investigation, accumulation of positive knowledge, minute methods of science and prolonged observation were alien to Greek temperament. These were introduced to Europe by the Arabs. European science owes its existence to the Arabs." Will Durant notes that Muslims "introduced precise observation, controlled experiment, and careful records."
Work of Muslims
Muslims were not alchemists, but rather they were the world's first true chemists. They produced a variety of compounds useful for the development and advancement of science, culture, industry, and civilization. Muslims invented and/or perfected the processes of distillation, sublimation, crystallization, oxidation, and precipitation. They discovered the process of calcination, which is used to reduce substances to a powdered form.
Muslims also discovered many elements with their specific weights. Al-Jabr (d. 815?) discovered 19 elements along with their specific weights. They also were the first to accurately divide the elements. Muslims distinguished between metals and alloys, noting that alloys were only mixtures and not true elements.
They originated the synthesis of numerous crucial substances that are essential to the development of chemical sciences. The acid-base principal of chemistry was entirely their development. The pH scale was their invention. Evidence is found in the fact that the word alkali originated from the Arabic word al-kili. They invented the concept of solutions regarding the solubility or insolubility of substances.
Industrial Chemistry
As industrial chemists, Muslims used advanced techniques for extracting minerals and metals. They perfected glass making and introduced the technology for coloring it with metal oxides. They invented crystal making. They introduced and perfected steel making. They produced dyes and used them in tiles, woodworking, and clothing. They produced a variety of plasters, glazes, and other building compounds. Muslim Spain had roads paved with cement instead of stones and had the world's first street lights.
Instruments
Muslims invented and/or widely used many chemical instruments that are used until now. They used burners, water baths, bellows, crucibles, distillation apparatuses, scales and weights, beakers, filters, flasks, phials, test tubes, etc.
Production of Paper
Muslims also perfected the production of paper. This accomplishment is often attributed to the Chinese. Though it is true that the Chinese produced paper, this was done through a tedious process requiring silk. It was the Muslims who instituted chemically-aided paper production. The first paper-manufacturing plant in the Muslim World was opened in Baghdad in 794 C.E. Millions upon millions of books were published wherever this invention arrived. In 891 C.E., Baghdad had over a hundred booksellers. Most mosques had libraries. Many cities also had public libraries. Baghdad at the time of the Mongols' invasion had thirty-six libraries. Private libraries were innumerable; it was common for rich people to have huge collections of books. Princes, according to Will Durant, "in the tenth century might own as many books as could be found in all the libraries of Europe combined."
Slowly but steadily, Europeans became accustomed to the luxury of imported paper from the Muslim world. Paper was used in Constantinople by 1100, in Sicily by 1102, in Italy by 1154, in Germany by 1228, and in England by 1309. The production of the many cheap books by Europeans was only possible after the replacement of parchment and silk paper with this new paper. The Western world slowly rose from the coffins of illiteracy in which it had been sinking.
Muslims' Writings and Books
Muslims' writings and books spurred and strongly stimulated the development of European chemistry. Translated versions of Al-Jabr's works were, according to Mathe, Lavoisier's "bible." Ar-Razi's (d. 925) booklet, Secret of Secrets, is said to be the first known example of a chemistry lab manual. Their books were used in many European schools for many centuries. After the Crusades, especially, as returning Western soldiers told fantastic tales of the Muslim World and all the knowledge that was there, Europeans wanted to learn more and their thirst for knowledge grew. Many books were translated into European languages. Slowly, the Western World acquired the knowledge of Muslims, and began its Renaissance.
Bibliography

1. Ajram, K. 1992. The Miracle of Islamic Science. Knowledge House Publishers.
2. Durant, Will. 1950. The Age of Faith. New York: Simon and Schuster.

taken from:
http://www.albalagh.net/kids/science/chemistry.shtml

history of chemistry

Chemistry is a branch of science that has been around for a long time. In fact, chemistry is known to date back to as far as the prehistoric times. Due to the amount of time chemistry takes up on the timeline, the science is split into four general chronological categories. The four categories are: prehistoric times - beginning of the Christian era (black magic), beginning of the Christian era - end of 17th century (alchemy), end of 17th century - mid 19th century (traditional chemistry) and mid 19th century - present (modern chemistry).

Time Intervals	Specific Times	Events	Description
Prehistoric Times - Beginning of the Christian Era (Black Magic) http://tqd.advanced.org/2690/hist/black.html	1700 BC	King Hammurabi's reign over Babylon	Known metals were recorded and listed in conjunction with heavenly bodies.
	430 BC	Democritus of ancient Greece	Democritus proclaims the atom to be the simplest unit of matter. All matter was composed of atoms.
	300 BC	Aristotle of ancient Greece	Aristotle declares the existence of only four elements: fire, air, water and earth. All matter is made up of these four elements and matter had four properties: hot, cold, dry and wet.
Beginning of the Christian Era - End of 17th Century (Alchemy) http://tqd.advanced.org/2690/hist/alchemy.html	300 BC -300 AD	The Advent of the Alchemists	Influenced greatly by Aristotle's ideas, alchemists attempted to transmute cheap metals to gold. The substance used for this conversion was called the //Philosopher's Stone//.
	13th Century (1200's) - 15th Century (1400's)	Failure of the Gold Business	Although Pope John XXII issued an edict against gold-making, the gold business continued. Despite the alchemists' efforts, transmutation of cheap metals to gold never happened within this time period.
	1520	Elixir of Life	Alchemists not only wanted to convert metals to gold, but they also wanted to find a chemical concoction that would enable people to live longer and cure all ailments. This elixir of life never happened either.
	End of 17th Century	Death of Alchemy	The disproving of Aristotle's four-elements theory and the publishing of the book, The Skeptical Chemist (by Robert Boyle), combined to destroy this early form of chemistry.
End of 17th Century - Mid 19th Century (Traditional Chemistry) http://tqd.advanced.org/2690/hist/traditional.html	1700's	Phlogiston Theory Coulomb's Law	Johann J. Beecher believed in a substance called phlogiston. When a substance is burned, phlogiston was supposedly added from the air to the flame of the burning object. In some substances, a product is produced. For example, calx of mercury plus phlogiston gives the product of mercury. Charles Coulomb discovered that given two particles separated by a certain distance, the force of attraction or repulsion is directly proportional to the product of the two charges and is inversely proportional to the distance between the two charges.
	1774-1794	Disproving of the Phlogiston Theory	Joseph Priestley heated calx of mercury, collected the colorless gas and burned different substances in this colorless gas. Priestley called the gas "dephlogisticated air", but it was actually oxygen. It was Antoine Lavoisier who disproved the Phlogiston Theory. He renamed the "dephlogisticated air" oxygen when he realized that the oxygen was the part of air that combines with substances as they burn. Because of Lavoisier's work, Lavoisier is now called the "Father of Modern Chemistry".
	1803	Dalton's Atomic Theory	John Dalton publishes his Atomic Theory which states that all matter is composed of atoms, which are small and indivisible.
Mid 19th Century - Present (Modern Chemistry or 20th Century Chemistry) http://tqd.advanced.org/2690/hist/modern.html	1854	Vacuum Tube	Heinrich Geissler creates the first vacuum tube.
	1879	Cathode Rays	William Crookes made headway in modern atomic theory when he used the vacuum tube made by Heinrich Geissler to discover cathode rays. Crookes created a glass vacuum tube which had a zinc sulfide coating on the inside of one end, a metal cathode imbedded in the other end and a metal anode in the shape of a cross in the middle of the tube. When electricity was run through the apparatus, an image of the cross appeared and the zinc sulfide glowed. Crookes hypothesized that there must have been rays coming from the cathode which caused the zinc sulfide to fluoresce and the cross to create a shadow and these rays were called cathode rays.
	1885	The Proton	Eugene Goldstein discovered positive particles by using a tube filled with hydrogen gas (this tube was similar to Thomson's tube...see 1897). The positive particle had a charge equal and opposite to the electron. It also had a mass of 1.66E-24 grams or one atomic mass unit. The positive particle was named the proton.
	1895	X-rays	Wilhelm Roentgen accidentally discovered x-rays while researching the glow produced by cathode rays. Roentgen performed his research on cathode rays within a dark room and during his research, he noticed that a bottle of barium platinocyanide was glowing on a shelf. He discovered that the rays that were causing the fluorescence could also pass through glass, cardboard and walls. The rays were called x-rays.
	1896	Pitchblend	Henri Becquerel was studying the fluorescence of pitchblend when he discovered a property of the pitchblend compound. Pitchblend gave a fluorescent light with or without the aid of sunlight.
	1897	The Electron and Its Properties Radioactive Elements	J.J. Thomson placed the Crookes' tube within a magnetic field. He found that the cathode rays were negatively charged and that each charge had a mass ratio of 1.759E8 coulombs per gram. He concluded that all atoms have this negative charge (through more experiments) and he renamed the cathode rays electrons. His model of the atom showed a sphere of positively charged material with negative electrons stuck in it. Thomson received the 1906 Nobel Prize in physics. Marie Curie discovered uranium and thorium within pitchblend. She then continued to discover two previously unknown elements: radium and polonium. These two new elements were also found in pitchblend. She received two nobel prizes for her discovery; one was in chemistry while the other was in physics.
	1909	Mass of the Electron	Robert Millikan discovered the mass of an electron by introducing charged oil droplets into an electrically charged field. The charge of the electron was found to be 1.602E-19 coulombs. Using Thomson's mass ration, Millikan found the mass of one electron to be 9.11E-28 grams. Millikan received the 1932 Nobel Prize in Physics for this discovery.
	1911	Three Types of Radioactivity	Ernest Rutherford sent a radioactive source through a magnetic field. Some of the radioactivity was deflected to the positive plate; some of it was deflected to the negative plate; and the rest went through the magnetic field without deflection. Thus, there were three types of radioactivity: alpha particles (+), beta particles (-) and gamma rays (neutral). By performing other experiments and using this information, Rutherford created an atomic model different from Thomson's. Rutherford believed that the atom was mostly empty space. It contains an extremely tiny, dense positively charged nucleus (full of protons) and the nucleus is surrounded by electrons traveling at extremely high speeds. The Thomson model was thrown out after the introduction of the Rutherford model.
	1914	Protons within a Nucleus	Henry Moseley attempts to use x-rays to determine the number of protons in the nucleus of each atom. He was unsuccessful because the neutron had not been discovered yet.
	1932	The Neutron Neutron Bombardment and Nuclear Fission	James Chadwick discovers the neutron. Enrico Fermi bombards elements with neutrons and produces elements of the next highest atomic number. Nuclear fission occurred when Fermi bombarded uranium with neutrons. He received the 1938 Nobel Prize in physics.
	1934	Artificial Radioactive Elements	Irene Curie and Frederic Joliot-Curie discovered that radioactive elements could be created artificially in the lab with the bombardment of alpha particles on certain elements. They were given the 1935 Nobel Prize.
	1940's	Manhattan Project	Albert Einstein and Enrico Fermi both warned the United States about Germany's extensive research on atomic fission reaction. Below the football field at the University of Chicago, the United States developed the very first working nuclear fission reactor. The Manhattan Project was in process.

Each link for each time interval contains some information about that period. Unfortunately, the information is sparse and the presentation of the info leaves much to be desired. However, more information on chemical history can be found in the links listed below. The list is collated in a chronological manner so like the table above, alchemy and black magic should be on top while traditional and modern chemistry should be closer to the end of the list. Also, there are some other links besides the ones that are in the time-interval section and these links should lead you to more information about the underlined topics.

taken from: http://www.columbia.edu/itc/chemistry/chem-c2507/navbar/chemhist.html